1. Field of the Invention
This invention relates to an apex seal device for use in a rotary piston engine, and more particularly to an apex seal specifically designed for preventing the blow-through of combustion gas from a combustion chamber into a suction chamber.
2. Description of the Prior Art
An apex seal for use in a rotary piston engine is attached to the crest of a rotor for sliding contact with the inner peripheral surface of a rotor housing of an engine, thereby maintaining air tightness between combustion chambers defined between the crests of the rotor and the inner peripheral surface of the rotor housing.
Accordingly, it is needless to mention that the apex seal should intimately contact the inner peripheral surface of the rotor housing. For this reason, the apex seal is loosely fitted within the seal groove defined in the apex or crest of the rotor in a radially movable manner, while there is provided a spring between the bottom surface of the seal groove and the apex seal for urging the apex seal against the inner peripheral surface of the rotor housing. In addition to this, the apex seal is urged in the same direction as above under a gas pressure in a combustion chamber, which pressure is introduced so as to act on the bottom of the seal groove.
However, the gas pressure acting on the bottom of a seal groove has some delay in timing, as compared with a rise in gas pressure in a combustion chamber. Thus, under the running condition of an engine having a combustion chamber which is encountered with a sharp or abrupt rise in the pressure, the gas pressure acting on the bottom of an apex seal fails to directly follow such a pressure rise, that part of combustion gas may blow around the tip of the apex seal into a suction chamber.
Hitherto, many attempts have been proposed to avoid such a shortcoming by providing slits and taper cuts in the side surfaces of the apex seal to thereby introduce a sufficient amount of gas from the combustion chamber onto the bottom surface of the apex seal, even if the apex seal is biased against the rotating direction of a rotor, due to the friction prevailing between the inner peripheral surface of the housing and the apex seal as well as due to the sharp or abrupt pressure rise within a combustion chamber. This, however, dictates the use of many man powers in manufacturing an apex seal which has the aforesaid slits or taper cuts, while failing to prevent the apex seal from being inclined. As a result, the blow-through of a combustion gas could not be prevented to satisfaction.